Method of call routing and connection

ABSTRACT

A method of radio communications and routing and connection in a mobile radio system consisting of the steps of providing nodes for transmitting and receiving signals wherein the nodes are positioned in a free form fashion within a defined area, and the routing of a communication is determined based on selecting the most desirable and normally the shortest path between the communication source and the destination drop.

[0001] This application is a continuation of U.S. patent applicationSer. No. 09/094,873 filed Jun. 15, 1998 which in turn was a continuationof Ser. No. 08\395,066 filed Feb. 27, 1995, now U.S. Pat. No. 5,793,842issued Aug. 11, 1998.

BACKGROUND OF THE INVENTION

[0002] The concepts of cellular radio are well known, and in fact allmajor metropolitan areas in the USA today enjoy cellular radio service.However, there are still vast areas in the USA, and also vast areas inthe world that do not yet enjoy cellular radio or any form of radiotelephone. The reason for this lack of service lays in the cost factorsassociated with conventional cellular technology. One of the mostexpensive elements in a cellular system is the central cellular switch.The central cellular switch controls channel choice, handoffs andconnection into the various land line carriers. The centralized conceptsassociated with cellular radio tend to be very expensive, and not veryflexible. Also a system using a central cellular switch requiresnumerous land line connections from the remote radio base sites (cellsites) to the central cellular switch. Land line connections arerequired for the desired communications links and also for the variouscontrol functions.

[0003] An approach for assigning channels in a decentralized system iscovered in U.S. Pat. No. 4,965,850 which is incorporated herein byreference. The present invention is an improvement over U.S. Pat. No.4,965,850.

[0004] The concept of having radios mounted on numerous telephone polessuch that the radios connect into the existing land line network hasbeen well publicized. For example, several articles have appeared in theIEEE by Donald Cox who was at Bellcore, the portion of Bell Labs thatwent to the regional Bells at the AT&T divestiture, at the time thearticles were written. The concept of the telephone pole radio systemimplies decentralization. The underlying assumption was that the localland line telephone company would take on the responsibilities of thecellular switch. However, a problem of that concept was that the variousexchange switches might not have the proper functionality, andadditionally the various exchange switches might be owned by anothercompany such that cooperative efforts would be difficult.

[0005] To implement the decentralized approach as described in thetelephone pole concept in a common carrier broad service environmentincluding vehicular service, the technology disclosed herein considersthe following factors. These factors relate to both technology and theoperating environment in which cellular operates and include:

[0006] 1. Relationship to existing land line carrier

[0007] 2. Call routing

[0008] 3. Call hand-off

[0009] Firstly, the relationship of the wireless company to the longdistance carriers must be considered. If, for example, in a currentcellular system, a wireless user in Northbrook, Ill. desires to contacta land line customer in New York, the wireless user in Northbrook willbe using at least four different companies to complete the call. One forthe airtime in the wireless network, another for the local phone companyin Illinois that provides control and communication links from thecellular switch to the Northbrook cell site, a third for the longdistance carrier, and fourth is the land line company in New York.Naturally, if it would be possible to easily eliminate the localtelephone company from the economic picture, the charges to the finalcustomer will be less.

[0010] The second factor considered relates to the call routing.Previously, there was no easy way for a call to be routed to a centralswitch without extensive land line charges from the telephone pole unitback to the central switch. Presently, the cellular operator takesresponsibility for call routing from its various base sites to hisswitch. Typically, the local cellular operator rents dedicated landlines from the local phone company. In some instances the local cellularoperator installs its own microwave links instead of renting variousland lines. When microwave links are installed, they replace thededicated phone lines. When the call is finally connected to the centralcellular switch, the cellular operator can connect the call from itscellular switch directly to a local phone company switch.

[0011] In an example of current technology, a wireless user in Zion,Ill. located near the Wisconsin border who desires to contact anotherland line user in Zion, Ill. will be using the Chicago system that has acellular switch located west of Chicago. The call must be routed fromthe wireless cell site in Zion to the Cellular Switch near Chicago, andthen back into the land line network through several exchanges(switches) to finally get back north up to Zion. Since Zion is locatedabout 50 miles from the cellular switch, this local call becomes a longdistance call.

[0012] The third factors relates to handoff control. If a vehicular userin Northbrook moves to a location served by an adjacent cell site, thecentral cellular switches in operation today would know how to handlethe handoff. In a decentralized system, there is a need to be able tocontrol handoff without either a central switch, or a hierarchicalsystem that might delegate handoff control to a local switch.

[0013] Consequently, there is a need for a system that would providedecentralized operation, without a large cellular central computer tocontrol the various base sites, and yet such that this system couldultimately connect to the various land line services.

[0014] S. Arunkumar and R. S. Panwar in an article entitled “EfficientBroadcast Using Selective Flooding” on page 2060 in the IEEE INFOCOMdiscuss methods of improving the efficiency of the signaling process inthe route establishment procedure. In their article they are referringto a US Army mobile subscriber system wherein nodes and links are in afreeform non-grid pattern. System nodes, transmitter and receiver sites,are connected to other nodes via point to point radio links. As nodesare moved around, different selective point to point links areestablished.

[0015] Although radio links between selected sites can be established byreferring to standard topographical maps, propagation charts, andantenna compass directions, such procedures are expensive and notflexible. Also, there is the possibility for human error in propagationcalculations, or map reading. At installation time, various antennashave to be pointed in specific directions. Also, if new sites arecreated or removed, then the entire system must be studied to ascertainthe impact of the changes. If buildings have been built that are not onthe maps, then selected radio paths will not work as planned.Consequently, there is need for a system that automatically establisheslinks based on the real propagation path, as opposed to establishinglinks based on some maps and calculations.

[0016] Preassigned channels for each given link requires carefuladjustment and careful installation. In fact, when a given radio site ismoved, there is seemingly no easy way to know which channels are beingutilized in other places in the system that might have propagation linkswith other unintended sites. Without this prior knowledge, there is noeasy way to guarantee a clear channel at any site. Accordingly, there isconsiderable value in having the channels automatically establishedwithout the possibility of interference between links.

[0017] A major practical problem in a mobile (remote) radio telephonesystem is to insure sufficient bandwidth to handle all of theconversations. With preplanned antennas and channel assignment, there isno flexibility to change around spectrum resources in response to systemload. In contrast, in the inventive system described herein, links areautomatically established based on signal strength; channels in theroute are assigned dynamically based on dynamic signal to interferencemeasurements thereby significantly increasing the call handling capacityof the system.

[0018] It is the purpose of this invention to offer a new technicalapproach for a mobile (remote) radio telephone system based on usingradio links to connect various sites into the land line network. Thisapproach will have several advantages over the conventional cellularequipment. Further, as the customer base builds, it will be easy toconvert some of the telephone pole sites to conventional “cell” siteswith a corresponding reduction in the amount of radio spectrum requiredto provide service. This invention will provide the possibility for newentrants into the cellular operations to cover wide geographic areaswith a very efficient system.

SUMMARY OF THE INVENTION

[0019] The invention herein describes a system and method of wirelesscall routing and channel assignment between various cell site locationssuch that the optimum route back to one of several telephone exchangesis chosen in an interference free manner. The invention further assignsradio communication channels dynamically whereby the available radiospectrum is shifted around.

[0020] The foregoing features and advantages of the present inventionwill be apparent from the following more particular description of theinvention. The accompanying drawings, listed hereinbelow, are useful inexplaining the invention.

DESCRIPTION OF THE DRAWINGS

[0021]FIG. 1 is a drawing of a hypothetical suburban area showing alimited number of nodes and a limited number of drop points nearexchanges;

[0022]FIG. 2 is a drawing showing the computer means, switching means,and radio means present at a typical node;

[0023]FIG. 3 is a drawing showing the network of FIG. 1, but addingadditional exchange drops for purposes of explanation;

[0024]FIG. 4 is a drawing showing a series of sites surrounding a largelake;

[0025]FIG. 5 is a diagram showing the receivers and transmitters thatare present in a remote, base site(s), and a drop (exchange) location;

[0026]FIG. 6 is a flow chart showing the steps in procedure 1 for thenode to remote link;

[0027]FIG. 7 is a flow chart showing the steps in procedure 2 for thenode to remote link;

[0028]FIG. 8 is a flow chart showing the steps in procedure 1 for thenode to node links;

[0029]FIG. 9 is a flow chart showing the steps in procedure 2 for thenode to node links;

[0030]FIG. 10 depicts a remote radio telephone system without a centralcontroller in accordance with the hand off feature of the invention;

[0031]FIG. 11 depicts the same system as in FIG. 11 with one of theremote users in a different place;

[0032]FIG. 12 is a flow chart showing the steps in test 1;

[0033]FIG. 13 is a flow chart showing the steps in test 2;

[0034]FIG. 14 is a flow chart showing the steps in test 3;

[0035]FIG. 15 is a flow chart showing the steps in test 4;

[0036]FIG. 16 is a diagram showing the transmitter and receiver channelsof a node for communicating with a remote;

[0037]FIG. 17 is a diagram showing the transmitter and receiver channelsof a remote; and

[0038]FIG. 18 is a diagram showing the transmitter and receiver channelsfor associated odd and even nodes;

DESCRIPTION OF THE INVENTION

[0039] The present invention discloses a decentralized call routingsystem and method for a node to node radio telephone communicationssystem. In the present invention, each individual node makes decisionsfor subsequent links based on information and signal strength derivedfrom the received signaling signal.

[0040] It is the purpose of this invention to provide a radio servicefrom the various cell sites to various desired drop points. Thesedesired drop points are located near associated exchanges. The presentsystem is totally self organizing. Previously, when radio links are usedinstead of land line phone lines to link cell sites to variousdestinations, careful system planning and design is required to insurethat each link has its private interference free channel, and thatspecific locations can communicate directly to other specific locations.It is the purpose of this invention to provide a system and method sothat cell sites can be placed anywhere, without a specific cell pattern,and that the routing and channel assignment to the desired exchangelocations though intermediate cell sites will occur automatically.

[0041] Definitions, Language Usage, and Basic System Concepts.

[0042] Cellular radio uses the term “cellular switch” to refer to thecentral controller that assigns channels, controls handoff, and connectsinto the land line network. The term “telephone switch” refers toswitches that are used to connect various incoming land lines to variousoutgoing land lines. In the cellular radio concept, the centralcontroller (cellular switch) is used to connect the land lines comingback from the cell sites to the land line telephone network.

[0043] Centralized systems are systems such as cellular radio that arecontrolled by a central controller. Decentralized systems such ascitizen band radio are not controlled by a central controller

[0044] There are three different types of functional units describedherein that contain radio equipment.

[0045] “Nodes” are radio units that contain the following components:

[0046] A) Radio transmitters and radio receivers to communicate withvarious remotes similar to todays cell sites.

[0047] B) Radio transmitters and radio receivers to communicate withother nodes perhaps similar in concept to repeaters.

[0048] C) Internal switching means to connect various receivers tovarious transmitters.

[0049] E) Internal computer means to perform functions and calculationstypically associated with on line computers.

[0050] F) Scanning receivers are also included herein. These receiversare controlled by the associated computer to move or monitor specificchannels.

[0051] G) Antennas

[0052] “Drops” are transmitting and receiving sites that connect to theland line phone network. These drops are related to the stationary halfof a consumer cordless phone. Drops are normally associated with a phoneexchange, and referred to also as “exchange drops”.

[0053] “Remotes” are radio units that are free to move about andtransmit and receive information. These remotes are related to mobiles,portables, cordless computer keyboards, and the movable half of aconsumer cordless phone.

[0054] Each node, drop, and remote has a unique identifier or code thatidentifies that particular unit.

[0055] Certain new technologies are available that would combine severalof the functions of the above components into a single a operative unit.However, for purposes of description of the functionality of the systemherein, the concepts are treated as separate hardware units.

[0056] For example, in an article in the November 1994 issue of CellularBusiness by Elliott Drucker, entitled “The Advantages of Broadband LPAs,the concepts of a linear power amplifier are presented. Druckerdescribes that tunable cavities and the various power amplifierspreviously present at a cell site can be combined into a single hybridcombiner and a single linear power amplifier.

[0057] In addition, Steinbrecker corporation, a Massachusetts supplierof radio equipment to the cellular industry, has combined many of themodulation and demodulation functions of separate radios into a singlecomputer like device. The combination of the two aforementionedtechnologies can give rise to cell sites that are quite small, and theconcept of fitting all of the equipment into a single “potato chip” canas described by Cox is available in today's hardware technology.

DETAILS OF INVENTION

[0058] Refer to FIG. 2. The nodes receive and transmit radio signals inresponse to computer information and received signals. These radiosignals can be directed to, or received from, various remote users inthe system, or to other nodes or drops that are within radio reach. Thedrops are positioned such that there is a maximum of one drop per landline phone exchange, and each drop or node can handle many simultaneousconversations. The maximum number of calls handled by a node or drop isonly limited by the radio spectrum available for the system.

[0059] As depicted in FIG. 1, the total path to complete the call isherein referred to as the route, and the individual segments of thatpath are referred to as links. Importantly, the nodes defined above aredivided into two categories, and for simplicity the nodes are designatedas odd and even numbered nodes.

[0060] In addition to the radio units that support the remote to nodecommunication, there is a separate and distinct radio/computer systemthat will route and connect the calls to various land line locations.This routing system is decentralized; there is no central control, andeach unit operates autonomously.

[0061] The present invention combines the concept of routing with theconcept of interference free channel assignment. This system furtherrelates the foregoing concepts with dynamic decentralized signal tointerference as explained in U.S. Pat. No. 4,965,850 and U.S. patentapplication Ser. No. 08/276781 filed Jul. 18, 1994 entitled“Decentralized Radio Communications System and Method for AssigningChannels with a Minimum of Signaling between Remotes and Bases” suchthat preplanning of cell locations to other cell locations is notrequired. Preplanning of the various links back to various drop pointsis not required. In fact, as various high traffic cells, ie sites, arechanged to permit land line connections back to the central switch, allof the hardware previously at that site can be moved intact to otherlocations, and the system will automatically adjust to its new location.

[0062] A central switch or central controller is not required in thepresent invention. This feature of no central computer or centralcontroller is a basic feature of the invention. Preplanning, frequencyselection, site to site propagation analyses are not required. Thesystem automatically adapts to the entrance of the new node, and callroutings and channel assignments for the call routings are handledautomatically. A technician merely has to climb the telephone pole,unscrew the unit from the telephone pole, and unplug the power source,and take the unit to a new location, and mount it to the telephone poleand plug it into the available power source. Additionally, thisinvention might be utilized in an existing installed centralized system.

[0063] As will be explained, the various nodes transmit information onvarious links, the nodes utilize this information, and retransmitinformation., The repetition of this process builds information in allof the nodes showing the optimum route from each node to each droppoint. Also importantly, this call routing information is created inadvance of any call set up or call connection process.

[0064] In the present invention for node to node communications omnidirectional antennas are used. The omni as used herein refers to thenorth south and east west directions, and not the up and down direction.The omni directional antennas are designed by well known procedures totransmit their lobes in a slightly less than the horizontal direction.Since all of the nodes are at about the same elevation above ground, anarrow beam can be utilized to provide significant signal gain.

[0065] Refer to FIG. 1 which shows a number of nodes in an example areain the United States. Although other exchanges and other nodes wouldnormally be present in the same area, only a few of the nodes andexchanges are shown for simplicity in explanation. FIG. 1 shows theconnection of a remote user in Deerfield to an exchange located in RoundLake. In this particular example, the remote user in Deerfield wants totalk to a land line customer in Round Lake with a 546 telephone prefix.Although the Deerfield user is near the Northbrook exchange, it isdesired to connect the user to the Round Lake exchange. This examplewill also be used subsequently to explain in detail the call set up andchannel assignment procedure.

[0066] Two types of nodes, designated as odd and even nodes, are used.The even numbered nodes transmit and receive on different bands than theodd numbered nodes. If all the nodes were identical, they would alltransmit in the same band, and receive in the same band; in thissituation, node to node communication can not occur. For node to nodecommunication, the bands must be reversed between the two units that arein communication. The spectrum for the node to node call routing andcommunication system is divided into several bands. The system designedherein is designed to operate at 1,900 megahertz. A band of frequenciesof 13 megahertz is used as follows. TABLE I Spectrum Band Name FunctionOdds Evens 1 Megahertz Sig Signaling T & R T & R 2 Megahertz A Node toDrop T & M T & M 2 Megahertz B Node to Drop R R 1 Megahertz C Node toNode T & M R 1 Megahertz D Node to Node R T 1 Megahertz E Node to Node RT & M 1 Megahertz F Node to Node T R 2 Megahertz G Remote to Node R R 2Megahertz H Remote to Node T & M T & M 0 Megahertz I Paging System

[0067] The bands above are a continuous spectrum of frequencies, and aresubdivided above for engineering design purposes.

[0068] In the Table I, the T stands for transmitting and the R standsfor receiving. M stands for the periodic messages that are transmitted,as will be explained hereinbelow. Bands A and B are paired with eachother, bands C and D are paired with each other, bands E and F arepaired with each other, and bands G and H are paired with each other.There term “paired” also means that channels are assigned inpredetermined pairs from each of the bands.

[0069] In Table I, the Sig Band is a signaling band that is used for theroute establishment process that will be explained herein. The Node toDrop bands A and B are used for communication to drops that function ascontrol points as will be explained herein. The bands A and B operate ina similar manner as the bands for communication with the remotes. BandsC,D,E, and F are used for communication links between nodes. Bands G andH are utilized to communicate between the remotes and the nodes.

[0070] Bands A and B are used to communicate from both odd and evennodes to the drops. The need for two bands to connect the nodes toeither a remote or a drop arises from the fact that it simplifies thesignaling process that occurs in performing the four tests as will beexplained herein below. In bands G and H the remote originates thesignaling process, and in bands A and B, the nodes originate thesignaling process.

[0071] Band I is used for city wide paging. This band functionsdifferently than band H, but is located in the top channel of band H.The design of paging systems is well known. Consequently, this band doesnot utilize any additional spectrum, and is indicated above as zeromegahertz.

[0072] Each of bands C,D,E, and F are one megahertz wide with channelsspaced 30 kilohertz apart. Each channel, after space for guard bands, isdesigned to carry the normal 3 kilohertz voice. There are 30 channels ineach of the above bands.

[0073] The exchange drops transmit on band B and listen on Band A fornode to exchange communications. Also, the final link in anyconversation will be to the land line drops.

[0074] Each node can communicate with approximately half of the totalnodes in the system; consequently, if the nodes were laid out in arandom manner, it would only be possible for a given node to talk tohalf of the other nodes. However, in a normal cellular/PCS system thenumber of possible routes is so high that the loss of communication to50% of the nodes at alternate links will not statistically cause aproblem.

[0075] The procedure of routing a call from a distant node back to alocal exchange comprises essentially two tasks. The first task is toestablish a route through various nodes that will ultimately connectback to the desired point. The second task is to assign channels alongthat route, so that interference does not occur.

Call Routing

[0076] The first task in connecting a call to a desired drop point is toestablish the route. In a cellular system, the location of the nodeswill be relatively permanent, and once a given node knows the route backto a particular drop point or particular exchange, this route should notchange unless a change occurs in the node layout.

[0077] Although the system might have a central switch similar totoday's central switch, the majority of calls are handled through localdrop units. These local drop units are similar to the central switch inthat they record call billing information, and route the call along.However, since they will handle only a limited number of calls, thereare much simpler in design and construction.

[0078] In the signaling band, all nodes can both transmit and receive.The signaling band is divided into a series of time slots. There are5,000 time slots in the signaling band. The first 1,000 slots arereserved for land exchange drops. The remaining 4,000 slots are reservedfor cell sites or nodes.

[0079] Each desired drop is given a sequential number between L1 andL999. These sequential numbers also correspond to the time slot number.Consequently, the maximum number of drops in the system is 999. In mostinstallations, the number of drops will be less than 50.

[0080] Each node is given a sequential number between 1001 and 5000. Thenodes that transmit in Band C are designated by odd numbers, and thenodes that transmit in Band D are designated by even numbers. Eachsequential number corresponds to a time slot number. Consequently, themaximum number of nodes that this system will support is 4,000. (Thenumber could be increased by minor expansion in the signaling time slotsthat will be explained hereinbelow.) In most installations, the numberof nodes will be less than 250, however, for purposes of explanation wehave used examples with larger capacities.

[0081] A master cycle comprises all of the time slots. Since in thisembodiment there are 5,000 time slots, the master cycle takes 5,000seconds. 5,000 second corresponds to somewhat over an hour. There isonly one channel in the signaling band. The channel is one megahertzwide.

[0082] The following table depicts a typical usage of the various timeslots arbitrarily given names of separate towns in Table II. TABLE IITime Slot No. User of Slot   1 L001 (Located in Round Lake)   2 L002(Schaumburg)   3 L003 (Evanston)   4 L004 (Glenview)   5 L005 (Lisle)  6 L006 (Libertyville) . . . . . .  27 L027 (Antioch) . . . . . . 10011001 (peoria node) . . . . . . 1133 1133 (Lincolnshire node) 1188 1188(Libertyville node)

[0083] The system provides periodic signaling once every four hours. Theperiodic signaling need not be timed for four hours, but may be anydesired time longer than the master cycle time. Each master cycle, aswill be explained below, will permit an increase in the number of linksin a route, and consequently to permit multilink routes, the mastercycle must be repeated. Signaling occurs to establish the routes fromall nodes to all of the concerned potential drops. This sequence ofseveral master cycles need only occur once, but occasionally nodes mightfail or lose power, so periodic checking insures better systemoperation. Each node signals in the time slot corresponding to itsnumber. For example, node 1143 would transmit during time 1143 duringthe signaling cycle.

[0084] In the particular example shown in FIG. 1 and FIG. 3, thefollowing is a list of some of the concerned exchanges and their typicalprefixes. All of the exchanges are in area code 708. TABLE III ExchangeLocation Area Code-Prefix-Number Round Lake 708-546-XXXX Round Lake708-740-XXXX Northbrook 708-480-XXXX Libertyville 708-362-XXXX Antioch708-395-XXXX

[0085] Step One of Call Routing

[0086] The first step is for the various drops to transmit a routingmessage in their unique time slot. The signaling channel is onemegacycle wide to permit high speed data transmission. The routingmessages are sent as sequential data streams through modems, as is wellknown. Each routing message contains the following: TABLE IV InformationExample Time Slot Number L001 Exchange Number L001 Prefix 546 LinkNumber “1”  1 Signal Strength 999 Exchange Number L001 Prefix 740 LinkNumber “1”  1 Signal Strength 999

[0087] The above example pertains to the transmission that would comefrom Round Lake. Since Round Lake has two different prefixes, twodifferent sets of information are transmitted. The link numbertransmitted is “1” as this will be the first link in the final routing.The signal strength, as will be explained hereinbelow corresponds to thenumber of Dbs over threshold. Since there is no received radio signal atthis point, the number 999 is transmitted.

[0088] Step Two of Call Routing

[0089] Although the number will vary, approximately twelve differentnodes might receive this transmission from Round Lake. Since nodeantennas are higher than remote antennas, it is usually the case thatnode to node communications occur over greater distances than remote tonode communications. A threshold level is set at each node receiver andsignals received less than 30 Db over threshold are excluded. Suchsignals are considered too weak to provide satisfactory service in apotential multiple link environment.

[0090] Refer to FIG. 3. For example, node number 1193 (Grayslake) mighthear and record the following messages received from various drops. Thesignal strengths and corresponding node and drop information, exchanges,prefixes, and link numbers are loaded into a computer memory table inthe node as follows: TABLE V 1193 (Grayslake) Exchange Prefix LinkSignal Strength L001 546 1 99 L001 740 1 99 L006 362 1 99 L027 395 1 99

[0091] The current measured signal strength is also added to the table.The table is now as follows: TABLE VI 1193 (Grayslake) Exchange PrefixLink Sig Str New SignalStrength L001 546 1 99 32 L001 740 1 99 32 L006362 1 99 43 L027 395 1 99 44

[0092] Note that in the above table only those drops having signalstrength over 30 Db are added to the table. In the above limitedexample, node 1193 (Grayslake) heard only three different transmissionsfrom drops. These three different transmissions contained a total offour different prefix numbers. As each transmission is received thesignal strength is measured, and the signal strength is recorded in thetable above.

[0093] Step Three of Call Routing

[0094] The next step in the procedure occurs in the next master cycle.Both nodes and drops transmit again. Each node transmits in its uniquetime slot all of the prefixes that it has heard. The nodes add their ownnumber and transmit all of the information in the above table. Forexample, node 1193 (Grayslake) would transmit the following during itsunique time slot. Since each node is adding a link to all tentativeroutes, the link number for each route is increased by one. Only aportion of the transmission is shown in table VII. TABLE VII 1193 Landnode number L001 Exchange number  546 Prefix   2 Link number  32Received signal strength L001 Exchange number  740 Prefix   2 Linknumber  32 Received signal strength L006 Exchange number  362 Prefix   2Link number  43 Received signal strength L027 Exchange number  395Prefix   2 Link number  44 Received signal strength

[0095] Step Four of Call Routing

[0096] Refer to FIG. 3. Various additional nodes hear the transmissionfrom node 1193. These additional nodes also hear transmissions fromother nodes in the different time slots. Each node then makes a table ofall the transmissions that it has received. Transmissions below 30 Dbare excluded. A portion of this table might appear as follows for node1188. TABLE VIII Table for Node No. 1188 (Libertyville) Node PrefixSignal Strength Link 1133 362 43 1 1193 546 32 2 1193 740 32 2 1193 36243 1 1194 546 50 2 1194 740 50 2 1195 546 31 2 1195 740 31 2

[0097] The above example, node 1188 heard messages from six differentnodes and drops. However, most were deleted as they were below the 30 Dbthreshold. Node 1188 also received useless messages back containingitself as a node in the route. In the previous cycle it had transmittedthat it related to exchange 362, and two nodes 1193 and 1133 havetransmitted that information back.

[0098] The left hand column above indicates the node from which thetransmission was received. The second column indicates the prefix thatwas with the transmission. The third column indicates the signalstrength that was in the message. The fourth column indicates the numberof links involved.

[0099] At this point the new signal strength being received is added tothe table as follows: TABLE IX Table for Node No. 1188 (Libertyville)Node Prefix Sig. Str. New Sig Str. Link 1133 362 43 43 1 1134 480 30 382 1193 546 32 43 2 1193 740 32 43 2 1193 362 43 43 1 1194 546 50 55 21194 740 50 55 2 1195 546 31 37 2 1195 740 31 37 2

[0100] At this point the node deletes from the table every message thatit has received from an even number node. Since 1188 is an even numberednode, it can not communicate with other even numbered nodes. If thisnode would have been an odd numbered node it would have deleted the oddnumbers. Since half of the nodes are even and half are odd, thisdeletion cuts the table in approximately half. Two of the nodes that1188 received from were even and they are deleted from the table. Thereason for this deletion will become apparent later as explained below.

[0101] The next step is to sort the table into prefix sequence, andconsequently, all of the messages with a selected prefix will be groupedtogether. For example, a portion of the above table would be as follows:TABLE X Table for Site No. 1188 (Libertyville) Site Prefix Sig. Str. NewSig Str. Link 1193 546 32 43 2 1195 546 31 37 2

[0102] The next step is to select only the best link for each prefix. Iftwo different routings contain a different number of links, the routingwith the minimum number of links is chosen and the routing with thehigher number of links is dropped from the table. Since only acceptablesignal strengths above the preselected 30 Db threshold are entered inthe table, this process selects a route with a minimum number of links.This procedure will reduce the number of transmitters that are radiatingpower and consuming spectrum capacity in the usage of the routes.

[0103] The next step is to drop all sub-optimal links. The links withinferior signal strength are dropped from the table. In the above table,the following is the worst link in each route: TABLE XI 1193 32 1195 31

[0104] In the above example, if 1188 (Libertyville) wanted to contactprefix 546, 1188 would have two choices. However, the route through 1193(Grayslake) provides the best signal strength, and consequently thatroute is chosen. The routes including 1195 are dropped from the table.The known Bellman principle of optimality indicates that an optimumrouting contains optimum sub routings. If two routings containedidentical numbers for both signal strength and links, the one with thelower position in the table is chosen.

[0105] One key point in the procedure above is that each node has thecapability, through storage in its computer memory, to provide at leastone route to all prefixes that can be reached with a signal greater thanthe minimum threshold as described above.

[0106] Step Five of the Routing

[0107] During the next master cycle, another transmission occurs asfollows. At this point, the computer in node 1188 (Libertyville)increases the link number in its internal tables. The next step is fornode 1188 to transmit the information in its computer memory table. Asexplained above, the node 1188 has already eliminated unsatisfactorylinks, and only transmits the best link for each possible exchange.

[0108] A portion of the transmission at this step is as follows: TABLEXII 1188 Land node number 546 Prefix 3 Links 32 Signal Strength

[0109] Note that node 1188 will also transmit the same messages aboutother exchange that were received via the same and other nodes.

[0110] Step Six through “n” in the Routing

[0111] Node 1133 receives the transmission from node 1188 and stores theinformation contained in the transmission in its memory. Node 1133 alsoreceives transmissions from other nodes and other drops near exchanges,which it also stores in its memory. Node 1133 then performs the samesteps that were performed by node 1188 to determine the optimum link toan intermediate node back to origin of prefix 546. This causes node 1133to delete from its memory all of the non optimum links, and thereby node1133 determines that the optimum route back to exchange 546 is throughnode 1188.

[0112] At this point, if a remote or mobile user in Deerfield wants touse his telephone, node 1133 is in a position to route a call to RoundLake to the 546 prefix.

[0113] Call routing 1133 can complete.

[0114] While node 1133 can not determine the total route, it candetermine the best immediate link for each exchange. Node 1133 does notstore the total route. During subsequent master cycles, the variousnodes again transmit in their selected time slots the various remaininglinks. The procedure continues to cycle as in the above steps.

[0115] At this point, after the routing process has been completed, anygiven node in the system has a table of the optimum routing throughother nodes to get to each individual prefix. For example in our aboveexample, node 1188 would have stored essentially permanently theinformation that the best way to route to the drop point near theexchange containing 546 would be through node 1193.

[0116] Since each node only transmits the preferred routing to eachprefix at an exchange drop, the number of transmissions that a singlenode will make is limited to the number of prefixes in the system. As anexplanation of this self limiting process, refer to FIG. 4 which showsan exchange drop L0047 and a series of nodes surrounding a large lake.Only a few nodes are shown to create a simple example. The node 1183 ison the far side of the lake relative to L0047. Let us assume in thisexample, that the lake is too large to permit propagation across thecenter of the lake. 1183 would receive from two different directionsinformation as to how to contact a prefix at the drop at near theexchange L0047. 1183 would save only the link to the node that was partof the optimum route based on signal strengths to the drop near theexchange L0047. When node 1183 would transmit the various routings backto the other nodes, they would note the increased number of links, anddrop the transmissions from their tables. However, 1183 would still knowthe best link that is part of the optimum route back to L0047.

[0117] Since the computerized sorting of the list of various links andselecting the preferred link will take some time, the node computer putsthe most recently received 5 messages into a buffer to permit thecalculations to begin five messages earlier. After the transmission, the5 messages are moved from the buffer into the associated table.

[0118] If a node fails, or has no power, it cannot transmit in theallocated time slot, and it will be excluded from any and all routes. Ifa node detects that any of its transmitter or receiver banks are notworking, it will exclude itself from the transmission in the allocatedtime slot. When a node excludes itself from participation in the callrouting process, it will be excluded from the call set up process.

[0119] Under normal operation of the system, the routes will be verystable. However, if a new node is added to the system, or an existingnode fails or is removed, the various routes and links will change.Reliability of the system may be enhanced by requiring all replacementlinks in the table of links in the node to be established twice insequence before deleting an older entry and adding a replacement entry.

[0120] Channel Assignment

[0121] When a remote or mobile user in Deerfield desires to contact aland line user in Round Lake, the call routing has already beenestablished. The Deerfield user now initiates a call.

[0122] It has been found that the process of using the various testsutilized in U.S. Pat. No. 4,965,850 above to assign channels createsexcellent spectrum usage with minimal interference. In contrast to U.S.Pat. No. 4,965,850 in the prior art, the act of just monitoring at onlyone of the two potential radios units, does not detect all of thepotential interference. Monitoring without comparison of desired andundesired signals usually implies setting of the threshold for channelreuse. If the threshold that will allow the channel to be reused, is setat a low number, a metropolitan area will have very little channel reusebecause the channel with very weak or distant signals on them willalways appear in use. If the threshold is set at a high number, the samearea will have interference because users will start using an activechannel without knowing it.

[0123] If two radio units are located in different places, they are eachsubject to a different set of potential signals that could interferewith them. They are also in a position to interfere with different setsof users. Also, frequently a channel is in use, but the new user pairhave such a good signal between them, that they can successfully reusethe channel without receiving interference. Also, the other users mighthave a good signal between them, and the new usage will not interferewith them.

[0124] The present invention discloses an improved method of connectingthe remote Deerfield user to a nearby node. This improved method isrelated to the method described in U.S. Pat. No. 4,965,850 herebyincorporated by reference. This improvement permits the reduction fromthe multiple tests described in U.S. Pat. No. 4,965,850 to a methodutilizing two procedures as will now be described.

[0125] Importantly, it was found that the first modification necessaryto utilize the present improvement is to increase the minimum signalquality for an acceptable communication from zero threshold to asignificantly higher value, say 30 Db.

[0126] The next important modification is to introduce a monitoring testat each of the node and the remote radios. Refer to FIG. 1 where theremote in Deerfield is trying to establish a communication path to node1133 in Lincolnshire. The tests set forth in U.S. Pat. No. 4,965,850that must pass in order to insure interference free channel assignmentare as follows:

[0127] Test 1 Will the transmission from the new node 1133 causeinterference with any other previously assigned remote receiver?

[0128] Test 2 Will the Deerfield remote receive an interference freesignal?

[0129] Test 3 Will node 1133 be interfered with by any other remotetransmitter?

[0130] Test 4 Will the Deerfield remote transmission interfere with anypreviously assigned node?

Inventive Procedure 1

[0131] The various nodes are continuously scanning the channels lookingfor usable channels. The messages and the scanning are synchronized suchthat the messages are transmitted for each channel in synchronizationwith the scanning for each channel. As the Lincolnshire node scans andmonitors a tentative channel, say channel R1, it measures the signalstrength received on that channel. The Lincolnshire node passesprocedure 1 if the measured signal strength is less than 10 Db overthreshold. If the it measured signal strength is greater than 10 Db overthreshold, the Lincolnshire node attempts another channel.

[0132] Refer to FIG. 6 for a flow chart of this procedure. The rationalfor this procedure is as follows. If the signal on the tentative channelis less than 10 Db over threshold it will not interfere with thereceiver at the Lincolnshire node, as the Lincolnshire node knows apriori that any desired signal will be stronger than 30 Db overthreshold. This automatically passes test 3.

[0133] If the undesired signal is less than 10 Db, the Lincolnshire nodeknows due to signal reciprocity that its transmission will arrive at theprior active users receiver at less than 10 Db. The Lincolnshire nodeknows a priori the other prior users are communicating at over 30 DBdesired signal level per the minimum acceptable level, the Deerfieldremote knows that it will not interfere with any other conversation, andthis passes test 1.

[0134] Consequently, this procedure passes both test 1 and test 3. Inboth test 1 and test 3 the desired to undesired signal ratio will bebetter than 20 Db. This 20 Db is sufficient for FM radio signals tocapture.

[0135] When the Lincolnshire node passes procedure 1, it begins totransmit periodic messages on the corresponding paired channel. Theseperiodic messages contain the node number and codes that say this is asignaling message indicating an acceptable channel.

[0136] Refer to FIG. 16 which shows the transmitter bank transmitting onband H (see Table I), and the receiver bank receiving on band G. If, forexample, the Lincolnshire node would have passed the procedure onchannel R1, the Lincolnshire node would be transmit on correspondingchannel T1. As mentioned above, the channels are paired.

[0137] Also, since a given remote might not hear this periodic messagebecause of interference, the Lincolnshire node steps to the next channel(R2), and repeats this procedure 1; that is, the Lincolnshire node stepsto the next channel and listens and measures the signal strength on thatchannel, and makes another decision. Consequently, if the Lincolnshirenode passes the procedure 1 for channel R2, it will also transmitperiodic messages on that corresponding channel (T2) simultaneously. Thenumber of simultaneous transmissions of these messages on differentchannels by the Lincolnshire node is limited to five channels.

[0138] This process of stepping through the channels and turning ontransmissions of messages will create several simultaneous transmissionson channels R1 . . . RN. When the node reaches the highest channel, theentire process is repeated, and new decisions are made for each channel.Thus the decisions for each channel are continuously refreshed.

[0139] In the meantime the Lincolnshire node is also monitoring thereceiver channel R1 of the paired channel T1,R1 corresponding to each ofits periodic messages. For example, if Lincolnshire is transmitting onT1, it would monitor R1 to determine if there is an acknowledgetransmission from a remote desiring communication on the channel pair T1and R1. It will know, as explained hereinbelow, that all four tests havepassed. The Lincolnshire node will than use that channel pair for thecommunication.

Inventive Procedure 2

[0140] The Deerfield remote knows that it must establish a link to anode. The Deerfield remote must choose a node and the Deerfield remotemust also choose a channel pair for communication to a node. Refer toFIG. 17. The Deerfield remote monitors a tentative channel, say channelR1 in band H, and measures the signal strength received on that channel.(Channel R1 for the remote is the same as channel T1 for the node.)

[0141] If the signal strength is below 30 Db above threshold, theDeerfield remote knows that an available node with an acceptable signalstrength is not signaling on this channel. Consequently, the Deerfieldremote monitors the next channel, say channel R2.

[0142] If the Deerfield remote hears a signal greater than 30 Db abovethreshold the remote analyzes this signal. The signal could be aperiodic message from a node on an available channel, or the signalcould be an unwanted communication using the channel. The Deerfieldremote senses this signal and determines if it is part of an ongoingcommunication or if it is a message signal indicating a potentialchannel. If this is an ongoing conversation, the remote steps to thenext channel. If this is a periodic message, then the remote knows ithas a tentative node and a tentative channel pair. The Deerfield remotenow listens in the time between the periodic message transmissions andmeasures the signal strength, if any, created by other users. If theseundesired signals are less than 10 Db over threshold the remote acceptsthis channel and this node as an acceptable choice. If these undesiredsignals are greater than 10 Db over threshold the remote steps to thenext channel.

[0143] Refer to FIG. 7 for a flow chart of this procedure. Therationalization for this decision is as follows. If the Deerfield remoteclearly heard a message signal on the tentative pair that is over 30 Dbabove threshold, the Deerfield remote knows that it will in fact receivea good communication signal on that channel. This passes test 2.

[0144] When the Deerfield remote listens in the time between theperiodic transmissions and hears a signal less than 10 Db over thresholdthe remote knows it would not interfere with that other user pairbecause the remote knows a priori that their desired signal is greaterthan 30 Db over threshold, and that due to signal reciprocity, this hissignal would arrive at less than 10 Db over threshold. This passes test4.

[0145] Consequently, this procedure passes both tests 2 and 4. Thepassing of these two tests will insure that the desired to undesiredsignal ratio will be at least 20 Db. This is sufficient for FM radiosignals to capture.

[0146] This remote, upon passing procedure 2, signals the desired node,and begins interference free communication.

[0147] As explained above, implementation of the two aforementionedprocedures will pass the tests and is sufficient to insure goodinterference free radio communications. It has been found that mostsystem users prefer a system busy signal, as opposed to getting anassignment that is very prone to channel disconnect due to interference.

[0148] In the present invention, the only requirement is that allongoing conversations be at least 30 Db over threshold, and that theprocedures eliminate channels that are have over 10 Db of signal onthem. In contrast, certain prior art required adding tones and digitaldata streams to all ongoing conversations for assuring interference freechannels.

[0149] The two procedures are most useful in areas where call quality isthe most important consideration. The previously described four testsprovide a very spectrally efficient method of assigning channels wherespectrum is very limited, and large numbers of users are anticipated.

[0150] Currently, the cellular industry is writing a number of standardsthat will permit multiple vendors to supply cellular systems componentsto the same customer. In addition, there are multiple standards beingwritten for the air interface. The air interface refers to the variousprotocols that are used to signal and utilize the radio spectrum such asfrom a mobile to a cellular base site. One of the ideas currently beingadded to the standards is the concept of the mobile participating in thechannel assignment process. The two procedures described above forchannel assignment are intended to be compatible with proposed airinterface standards.

[0151] When a user contacts a node and desires to call a number forwhich there is no prefix in the node computer, the land node routes thecall to the exchange drop with the least number of links. Although thepreferred embodiment for this invention is to work with multipleexchanges at different locations each with multiple prefixes, theinvention can be used with a single exchange having multiple nodes.

[0152] Because a remote user is routed directly to the exchange carryingthe desired prefix, land line charges will be minimal. Land line phoneusers typically under selected calling plans, get free calling within acertain radius. Consequently, in this example, if the remote user inDeerfield would have routed to the closest exchange drop in Northbrook,the user would have been subject to land line charges from Northbrook toRound Lake. However, in this particular example, the user would connectdirectly to Round Lake, and avoid the long distance charges from thelocal phone company.

[0153] Since the physical location of the nodes is not part of therouting procedure, the call routing system will work with nodes ineither standard grid patterns or in patterns that might be chosen basedon other criteria.

Call Connecting and Channel Assignment

[0154] The process of using the previously created routing informationin conjunction with measured signal strengths that connects the callbetween nodes will now be explained.

[0155] The invention addresses the channel selection process andconsiders the following factors:

[0156] a) Nodes can not transmit and receive in the same band

[0157] b) Channels must be assigned in pairs

[0158] c) Call set up must be prompt

[0159] d) Channels chosen must not cause interference

[0160] Channels chosen must not receive interference

[0161] In the example of FIG. 1 the remote user in Deerfield wants toconnect to phone number prefix 546 which is handled by the Round Lakeexchange. The first step is for the Deerfield user to establishconnection with a node near Deerfield with an acceptable signal qualityand interference situation. This connection has been explained above. Inthe example in FIG. 1, this radio connection is made with node 1133.Once this connection is established, the node 1133 now must begin theprocess of connecting the call to Round Lake. As explained above, node1133 has in its memory the node it must contact to establish the firstlink in the route to Round Lake.

[0162] Refer now to FIG. 5 which shows, in additional detail, thecommunications paths between a mobile (remote) user in Deerfield and adrop near the exchange in Round Lake that handles the phone numberprefix 546. As will be appreciated, the land drop will connect to theRound Lake exchange by standard land line methods.

[0163] Each of the odd numbered nodes, 1133 and 1193, contains thefollowing components: TABLE XIII A1 Signaling transmitter (TR) for callrouting procedure A1 Signaling receiver (R) for call routing procedureA2 TR for voice communication to a remote A2 R for voice communicationfrom a remote A3 TR for voice communications to exchange A3 R for voicecommunications from exchange A4-O TR for sending voice communicationsfrom node to node for remote originated voice A4-O R for receiving voicecommunications from another node for exchange originated voice A5-O Rfor receiving voice communications from another node for remoteoriginated voice A6-O TR for sending voice communications to anothernode for exchange originated voice

[0164] The even numbered nodes (1188 in FIG. 5) contain the same numberof components, but the node to node transmitters and receivers arereversed to transmit and receive in different bands as indicated above.Thus each of the even numbered nodes contains the following components:TABLE XIV A1 Signaling transmitter (TR) for call routing procedure A1Signaling receiver (R) for call routing procedure A2 TR for voicecommunication to a remote A2 R for voice communication from a remote A3TR for voice communications to exchange A3 R for voice communicationsfrom exchange A4-E R for receiving voice communications from node tonode for remote originated voice A4-E TR for sending voicecommunications to another node for exchange originated voice A5-E TR forsending voice communications to another node for remote originated voiceA5-E R for receiving voice communications from another node for exchangedrop originated voice.

[0165] The system and method for setting up a call through various nodesare related to the method described above for connecting the remote tonode. FIG. 5 shows the example of a call between a mobile (remote) userin Deerfield and an exchange drop in Round Lake that is being routedthrough a total of three different nodes. The new process of setting upthe call between multiple nodes will be explained hereinbelow. Althoughthe channels in the above tables and FIG. 5 are designated as voicechannels, various data can be transmitted through such channels as iswell known.

[0166] As indicated in FIG. 5, for the node to node communication bands,the odd nodes have transmitters which operate in the bands where theeven nodes have receivers. Conversely, the odd nodes have receiverswhich operate in the bands where the even nodes have transmitters.

[0167] As will be more fully explained herein, the mobile (remote) canoriginate communications on channel pair say 1 in bands G and H, and thecommunications from node 1133 to node 1188 will be on a channel pair say14 in bands C and D, and the communications from node 1188 to node 1193will on a channel pair say 17 in bands E and F, and the communicationsfrom node 1193 to the drop of exchange including prefix 546 will be on achannel pair say 3 in bands A and B.

[0168] Tests are performed to ascertain that any channel choice will beboth interference free and non interference causing. The channels chosenconform to the route as explained above.

[0169] Referring still to FIG. 5, the first step in the process is forthe first node, in this case node 1133 located in Lincolnshire toestablish a link with the next node. To facilitate this explanation, letus assume the following is the optimum route: TABLE XV Mobile (remote)user in Deerfield Node 1133 located in Lincolnshire (Odd) Node 1188located in Libertyville (Even) Node 1193 located in Grayslake (Odd) Droplocated in Round Lake Exchange located in Round Lake

[0170] In the present system nodes are deployed in sufficient quantityto provide good radio coverage to the remotes. Nodes are given extraantenna height, extra power, and nodes are deployed in sufficientdensity to insure good radio coverage, and node to node communication isusually not limited by poor propagation paths. In the present invention,the nodes are located in a random manner or manner dictated by providinggood radio coverage to remotes and interference between nodes could be aproblem. However, by a unique system, and method of operation, thepresent invention provides interference free node to node communication,as will be explained hereinbelow.

[0171] As in the remote to node channel assignment procedure describedabove, the minimum acceptable signal strength for node to nodecommunication is set at a high threshold of say, 30 Db.

[0172] Refer to FIG. 1 where Lincolnshire node 1133 is trying toestablish a communication path to node 1188 in Libertyville. The fourtests as mentioned above are used again specifically as follows:

[0173] Test 1 Will the transmission from node 1133 interfere with anyother node reviver?

[0174] Test 2 Will node 1188 receive an interference free signal fromnode 1133?

[0175] Test 3 Will node 1188 interfere with any other node receiver?

[0176] Test 4 Will node 1133 receive an interference free signal fromnode 1188?

Procedure 1

[0177] Refer to FIG. 18. Node 1133 knows that it must establish a linkto node 1188. Node 1133 monitors a tentative channel, say channel R1 inband D, and measures the signal strength received on that channel.

[0178] Node 1133 passes procedure 1 if the measured signal strength isless than 10 Db. If the measured signal strength is over 10 Db, node1133 attempts another channel.

[0179] Refer to FIG. 13 for a flow chart of this procedure. Therationale for this procedure is as follows. If the undesired signal isless than 10 Db it will not interfere with the receiver at node 1133, asnode 1133 knows a priori that the desired signal will be stronger than30 Db. This automatically passes test 4.

[0180] If the undesired signal is less than 10 Db, node 1133 knows dueto signal reciprocity that its transmission will arrive at the activeusers receiver at less than 10 Db. Since the other users arecommunicating at over 30 DB desired signal level, node 1133 knows thatit will not interfere with any other conversation, and this passes test1. Consequently, this simple procedure passes both test 1 and test 4.

[0181] If 1133 passes procedure 1, it begins to transmit periodicmessages to node 1188 on the tentative channel in the pair. Thistransmission occurs in band C. TABLE XVI Description of partial contentsof periodic message Originating Node 1133 Next Node in Routing 1188Phone number of remote YYYYYYYY Desired Destination number 708-546-XXXX

[0182] Also, since 1188 might not hear this periodic message because ofinterference, node 1133 steps to the next channel R2, and repeats thisprocedure; that is, the node 1133 steps to the next channel R2 andlistens and measures the signal strength on that channel, and makesanother decision. Consequently, if node 1133 passes the procedure 1 forchannel R2, it will also transmit periodic messages on thatcorresponding channel (T2) simultaneously, The number of simultaneoustransmissions of these messages on different channels by the node 1133is limited to five channels.

[0183] Node 1133 also monitors the receiver channels in band D on thereceiver channels paired to its message transmissions. For example, ifit is sending a message on channel T1 in band C, it will be monitoringchannel R1 in band D. If it hears a transmission from 1188 (as will bedescribed below), the link is established. When 1133 hears a messagefrom 1188, it cancels its other tentative transmissions.

Procedure 2

[0184] Node 1188 is monitoring potential channels in band C for a linkfrom an arbitrary node. If node 1188 hears a good signal from node 1133on a particular channel, then node 1188 measures the signal strength inthe period between the periodic transmissions. If the signal in theperiod is less than 10 Db over threshold, then node 1188 accepts thechannel and signals back to node 1133 on the corresponding channel inband D that they have established communications. If the signal in theperiod between transmissions is over 10 Db over threshold the channel isnot accepted, and node 1188 monitors other channels. If node 1188 cannot hear this transmission from 1133, 1133 will in the meantime monitorother channels.

[0185] When node 1188 hears a good transmission, it has passed test 2.

[0186] When node 1188 measures the signal strength in the period betweenperiodic messages and learns that it is less than 10 Db over threshold,node 1188 knows it will not interfere with the other users. Due tosignal reciprocity, the received signal from node 1188 at the otherusers receiver would be less than 10 Db over threshold. Node 1188 knowsa priori that the other desired signal is over 30 Db over threshold.Consequently, node 1188 knows it will not interfere with that previoususer. This passes test 3. Refer to FIG. 14 for a flow chart of thisprocedure.

[0187] Thus, implementation of the two aforementioned two procedureswill pass the four tests.

[0188] Furthermore, the requirement of adding tones and digital datastreams to all ongoing conversations is eliminated. The only requirementis that all ongoing conversations be at least 30 Db over threshold, andthat the procedures eliminate channels that have a signal over 10 Dbover threshold.

[0189] As alluded to above, the node to node communications bands areBands C,D,E, and F. The selection of a channel pair between node 1133(Lincolnshire) and node 1188 (Libertyville), is independent of whethernode 1133 received this routing demand from a remote or from anothernode. The routing and channel selection process works such that therouting and channel selection process originates with node 1133 andworks towards node 1188 and node 1193.

[0190] Channel Assignment for the Second and Following Node to NodeLinks

[0191] The process that node 1188 (Libertyville) goes through toestablish channel selections with node 1193 (Grayslake) are identical tothe processes just described. However, since node 1188 is an even numbernode, it does its scanning and tentative transmissions in a differentpair of bands. Site 1188 will tentatively transmit in band E and listenin band F.

[0192] Once the call reaches the final node 1193 (Grayslake), it isconnected to the drop near the Round Lake Exchange in a manner similarto that described above in the node to remote communication. In theprocess of connecting a node to a drop, the direction of control is fromthe node to the drop, This direction is the reverse of the directionthat is used to connect a remote to a node. The method is essentiallysimilar to the method used to connect the remote to the node, but thecall and control is initiated in the node. Two separate bands (Bands Aand B in Table I) for node to drop is included as described above in thesystem. As will be appreciated, the remote to node signaling andcommunication is placed inn one pair of bands, and the node to dropsignaling and communication is placed in another pair of bands.

[0193] If a node receives a connection from a remote that desires tocommunicate with a prefix that is not in the routing table, the nodewill connect the call to the drop with the least number of links in theroute as described above. Since the computer in each node knows thenumber of links to each drop, the computer can choose a nearby drop. Ineffect when a call arrives for a new prefix, the computer hasestablished a route to a nearby drop and the call is processed as above.

[0194] If the operator of the wireless system described herein wants toavoid using the local phone company for long distance calls, the dropsto the connection points to the long distance carrier would participatein the route establishment procedure as described above. They would usean arbitrary prefix such as 900 to indicate a drop for connection tolong distance.

[0195] In most installations of the above system; the system will beinstalled in a single area code. However, to install a system in an areathat is serviced by multiple area codes, the area code and the prefixmust be utilized together as a single destination in the routing asdescribed above.

[0196] Handoff

[0197] When an active remote user such as a vehicular user moves fromone geographic area to another area, his call is handed off betweennodes. Hand off is an important part of the present system, and isperformed when signal quality or signal strength falls below apredetermined level. Handoff involves the process of disconnecting amobile (remote) user from one node, and connecting the mobile (remote)user to a second node. The node with the strongest signal is selected toreceive the handed off call.

[0198] In certain prior art a central controller or central switch isemployed in the handoff process. In certain other prior art a centralprocessor and local area controllers control the handoff process. Thiscentral controller and local area controllers are in addition to theregular land line telephone switch. This second switch or second switchand associated local controllers are expensive, and they are part of thereason for the high air time cost of cellular radio today. There havebeen proposals that the various land line telephone switches assumeresponsibility for the hand off process. However, in many radiotelephone systems, the land line telephone switch is owned by onecompany, and the cellular radio system is owned by a second company.Without standardization, regulation, and cooperation, the possibility ofusing the regular land line telephone switch to handle cellular radiofunctions seems difficult.

[0199] Because of the complexity and high cost of the multiple switchesto provide mobile radio telephone service, various industry sources haveindicated that a decentralized system similar to today's cordless phonesbe employed as an alternative to today's centrally controlled systems.Such a decentralized system would have no central computer or controllerand would function without any central control.

[0200] The present invention includes a system and method for handoff ina decentralized system without the aid of either a cellular switch or acooperative land line switching center. The handoff is accomplished byproviding all the needed information to one of the nodes or exchangedrops. The exchange drops and nodes then can control the handoffprocess.

[0201] For the handoff procedure, each node and drop keeps a list ofactive conversations that includes the phone number of the concernedremote. Technology for the maintenance of an online data base is wellknown.

[0202] Refer to FIG. 10. FIG. 10 shows mobile (vehicular) mobile user 2making a call through node 1192. These drops are positioned such thatthere is a maximum of one drop per land line phone exchange. Each dropor node can handle many simultaneous conversations. The maximum numberof calls handled by a node or drop is only limited by the radio spectrumavailable for the system. Land line phone exchanges are well known phonecompany local switches. Mobile (remote) user 1 and mobile (remote) user2 two contain transmitters and receivers units required to make a radiotelephone call.

[0203] Note that the connection between user 2 and node 1192 is a radiolink, as are all other links in the system of FIG. 10. Also note thatUser 2 is talking to the 223 exchange, and is being routed from Node1192 to Node 1191 to Node 1188 and onto the exchange drop for 223.

[0204] User 2 to Node 1192 to Node 1191 to Node 1188 to Exch drop 223

[0205] Also note that user 1 is making a call to the 546 exchange and istalking to Node 1133 which is in turn connected to Node 1188 and to Node1193 onto exchange drop for 546.

[0206] User 1 to Node 1133 to Node 1188 to Node 1193 to Exch drop 546

[0207] Note that Node 1188 has two different calls each going todifferent destinations. This example typifies the type of complexitythat occurs in large systems.

[0208] Now, let us assume that User 2 is moving away from Node 1192 andgetting closer to Node 1190. His signal quality is decreasing, and heconsequently needs a handoff.

[0209] User 2 follows the call initiating procedure as recited above.User 2 determines, per the procedures described above that he needs anew channel, and that the Node 1190 should be utilized.

[0210] Node 1190 accepts the call. Node 1190 notes that this call is tobe directed to exchange 223 and consequently to the exchange drop for223. At this point node 1190 does not know if this is a new call thathas to be routed to exchange Drop for 223, or if this is a handoff thatneeds to be routed to exchange Drop 223. Based upon the proceduredescribed above for routing, Node 1190 does know that it has to route toNode 1191. Therefore, Node 1190 establishes a new interference freeradio link to Node 1191 as described above. Consequently, Node 1191 nowhas established the link from Node 1191 for Mobile User 2.

[0211] However, before Node 1191 continues to route the call per therouting procedure as described above, Node 1191 performs the step ofchecking through a list of calls in process. Node 1191 searches his listof calls for a matching phone number of the new mobile, remote user 2.If Node 1191 recognizes this user as being part of another call inprocess, then Node 1191 knows that it must perform a routingmodification. Consequently, Node 1191 connects the new audio or datasignal coming from Node 1190 and disconnects the old audio for this usercoming from Node 1192.

[0212] This completes the handoff procedure. Note that there is only onedrop point per each exchange. If multiple drops were to access a singleexchange, it is possible that a new route established as a result of ahandoff would not use the same nodes, and consequently, the list searchmentioned above would not show that this was a call in process, andhandoff and substitution need would not be detected.

[0213] All nodes and drop points perform this list search step ofsearching for existing conversations involving any new call.Consequently, the handoff and signal substitution can be performed byany one of the nodes along the radio route, and also the handoff andsignal substitution can be performed by the drop. Since the procedureinsures that the handoff is controlled as near as possible to theremote, many times radio links nearer the drop point are not eveninvolved and nodes and drops near the exchange are not aware that ahandoff occurred. Accordingly, the complete route set up need not beperformed.

[0214] Now, refer to FIG. 11. FIG. 11 shows that Mobile User 2 hascontinued to move, and that he is now leaving the vicinity of Node 1190and arriving in the vicinity of Node 1193. Because the received signalfrom Node 1190 is getting weak, a handoff is indicated. Mobile User 2now begins the procedures as explained above. Mobile User 2 now sets upthe call through Node 1193. Node 1193 now performs the radio routing asexplained above. This is a new call to Node 1193, so node 1193 routesthe call on to Node 1188. Node 1188, however, recognizes the mobile(remote) number as previously having a conversation coming in from Node1191. Consequently, Node 1188 disconnects the call from Node 1191, andconnects the call coming in from Node 1193. The call is continuouslyrouted to the exchange drop for 223. This completes the handoff.

[0215] Note that the first handoff was controlled at Node 1191 when themobile (remote) moved from the vicinity of Node 1192 to Node 1190. Thesecond handoff was controlled by a different node, in this case Node1188, when the mobile (remote) moved from Node 1190 to Node 1193. Notethat this procedure does not effect Mobile 1 who is routing through Node1133 and Node 1188 onto Node 1193 onto the drop for 546.

[0216] Land Line Originated Call

[0217] In the previous example, a remote (mobile) user in Deerfieldinitiated a phone call to a land line user in Round Lake. We nowdescribe the process for a land line user in Round Lake to initiate acall to a remote (mobile) user in Deerfield.

[0218] In today's cellular the central switch is given an exchangenumber. When a land line user wants to call a cellular user he dials thephone number of the cellular user which includes the exchange number ofthe cellular central switch. The call is then connected to the cellularswitch which handles the call set up process. In the decentralizedsystem described herein, each remote user in the system is given aunique number with the prefix corresponding to an exchange numbercorresponding to the decentralized system. However, any one of the droppoints will suffice for the call set up process. Consequently, when theland line user dials the decentralized exchange number, the local landline exchange merely connects to one of the nearby drops. This savesland line charges in that the call is connected locally to thedecentralized system.

[0219] The drop and the Deerfield mobile, then perform the followingsteps:

[0220] a) The drop temporarily holds the call

[0221] b) The drop pages the user city wide

[0222] c) The Deerfield remotes initiates a call

[0223] c) The Drop connects and completes the call

[0224] Step a. When a drop receives in incoming call for a remote user,the drop temporarily holds the call.

[0225] Step b. With another outgoing land line, the drop connects to thecity wide paging system, and the drop sends the paging system a pagemessage containing an exchange number at the drop and an arbitraryfictitious phone number within the exchange. For example, the droplocated at Round Lake would send the following message to the pagingcomputer:

[0226] a) Exchange 546

[0227] b) Number 0000 or perhaps A001

[0228] c) The number of the remote (now in Deerfield)

[0229] The city wide paging system then broadcasts over the entiremetropolitan area the paging message contents listed above.

[0230] Step c. The Deerfield remote, upon receiving the page, theninitiates a call in an identical manner to when the Deerfield remotewere the initiating party.

[0231] Step d. When the Deerfield call finally is routed to the correctdrop, the drop notes the artificial phone number, and connects theDeerfield call back to the proper land line user.

[0232] Remote User Calling Remote User

[0233] When a remote user in Round Lake desires to call a remote user insome unknown location, the Round Lake remote user enters the itdecentralized system in the manner described above. However, the firstnode notes that the phone number corresponds to a remote phone in thedecentralized system. The first node then routes the call to the nearestdrop.

[0234] The nearest drop then proceeds in an identical manner as if for aland line initiated call including the holding and paging processdescribed above. When the call comes back from the remote in the unknownlocation, the drop then connects the call.

[0235] Roaming

[0236] When a drop initiates a page, and the remote user does not comeback in the form of a routed call, the drops knows that the unit isinoperable, or that the unit has roamed out of town. The drop thencontacts central data base of roamers and asks for the location of thedesired mobile. The drop then can either inform the calling party thathis desired remote is inoperable, or else the drop can connect the callto the correct out of town switch.

[0237] When an out of town user arrives in town, the out of town usernotifies the closest node of his presence, and that node sends thatinformation to a drop by setting up a short duration phone call in themanner described above. The drop then notifies the central data base ofroamers that the out of town user has arrived in this area. Now, anyland line phone call directed to any one of the local drops can page anout of town user and set up a call.

[0238] In a large metro area like Chicago metro area, several differentarea codes are involved. The drop actually notifies the central database of roamers which area code to use to connect to the decentralizedsystem.

[0239] It takes a minimum of two different types of nodes such thatcommunication can occur. In the preferred embodiment two different typeshave been chosen; in other embodiments, three or more different typesmight be chosen. In the two type configuration, the odd nodes cancommunicate with the evens and the evens can communicate with the odds.

[0240] Customer Billing

[0241] Customer billing systems are well known. In this particularinvention each of the drops keeps a record of all calls. The drop arepolled by a billing system as is well known, and a centralized billingsystem implemented.

[0242] Embodiment B

[0243] Another application of this invention occurs in large corporatecomplexes. Frequently, in large corporate complexes, there are severalbuildings involved, and thousands of employees. Many of these employeeswant to carry Personal Digital Assistants better known as PDAs. PDAs arebasically a combination of a computer and a radio link.

[0244] In the corporate complex application, there are multiple digitalcomputers that are referred to as host computers. These computerscorrespond to the drop points in embodiment A. Also, there are multiplePDAs that correspond to the remotes in embodiment A.

[0245] Each host computer is given a unique identified that correspondsto the exchange and prefix number in embodiment A.

[0246] The nodes as described in embodiment A are called repeaters inthis embodiment. These repeaters are placed in the corporate complexsuch that all important areas are given good radio coverage. Because ofthe problems of radio communication in buildings caused by steelreinforced concrete walls and floors, many repeaters must be installed.Typically, a repeater is installed in each large room.

[0247] To permit complex wide communication, repeaters are installedsuch that each repeater can view at least one other repeater of theopposite odd/even designation.

[0248] In the corporate complex a complete communication system can thusbe installed that will permit any PDA to contact any host computer. AnyPDA can contact any host computer by merely indicating the number of thehost computer.

[0249] Because the bands used by the host computers are different fromthe bands used by the PDAs, host computers can not contact hostcomputers directly, and PDAs can not contact PDAs directly. However,host computers that desire to contact other host computers, can installa second bank of transmitters and receivers with the extra bands suchthat the host computer would initiate communication as if it were a PDA.

[0250] Embodiment C

[0251] Embodiment C provides a channel assignment which is related tothe above described routing and two procedure system, and in additionincludes additional specific tests for assuring free channel assignmentas might be required in a more congested or populated area.

[0252] Embodiment C uses a decentralized signal to interference methodas explained in U.S. Pat. No. 4,965,850 and improved in U.S. patentapplication Ser. No. 08/276781. As with the two procedure systemdescribed above preplanning of the various links back to various droppoints is not required. Basically embodiment C is the same as embodimentA, and the two embodiments operate similarly, except that in thisembodiment four detailed tests are used to determine if a channel can beused without interference. This change will permit greater frequencyreuse and greater spectrum capacity. This change will also allow linkswith signal strength below 30 Db to be used satisfactorily.

[0253] In the following explanation, in order to avoid duplication, onlythe differences between the two embodiments will be emphasized. Asmentioned above, the two embodiments are similar.

[0254] Refer to FIG. 1 which shows a number of nodes in an example areain the United States. In the explanation of this embodiment, thepropagation losses are assumed to be as shown in the following tables.Note that the following table, Table XVII, is slightly different thanTable I. As described above with respect to the two procedure embodimentit is assumed that a remote user in Deerfield wants to contact a RoundLake exchange. TABLE XVII Spectrum Band Name Function Odds Evens 1Megahertz Sig Signaling T & R T & R 2 Megahertz A Node to Drop T & R T &R 2 Megahertz B Node to Drop R R 1 Megahertz C Node to Node T & Q R 1Megahertz D Node to Node R T 1 Megahertz E Node to Node R T & Q 1Megahertz F Node to Node T R 2 Megahertz G Mobile to Node R R 2Megahertz H Mobile to Node T & Q T & Q

[0255] Table XVII is generally similar to Table I, however, Table XVIIincludes Q which refers to the transmissions that occur in theimplementation of test 1 as will be described herein.

[0256] In the above Table XVII, the bands for radio communication areshown. The Sig Band is a signaling band that is used for the routeestablishment process that will be explained herein. The Node to Dropbands A and B are used for communication to drops that function ascontrol points as will be explained herein. The bands A and B operate ina similar manner as the bands for communication with the remotes. BandsC,D,E, and F are used for communication links between nodes. Bands G andH are utilized to communicate between the remotes and the nodes.

[0257] Call Routing

[0258] The first step in connecting a call to a desired drop point is toestablish the route. It should be noted again that the nodes can beplaced in any pattern, and need not be placed in a grid pattern. This isan important feature of the invention in that nodes can be placedanywhere. When nodes have to conform to a grid pattern, available sitesmay not be present at the desired location.

[0259] As described above, in the signaling band, all nodes can bothtransmit and receive. The signaling band is divided into a series oftime slots. There are 5,000 time slots in the signaling band. The first1,000 slots are reserved for land drops or exchanges. The remaining4,000 slots are reserved for cell sites or nodes.

[0260] Each desired drop point is given a sequential number between L1and L999. These sequential numbers also correspond to the time slotnumber. Consequently, the maximum number of drop points in the system is999.

[0261] Each node is given a sequential number between 1001 and 5000.

[0262] The following table which has been abbreviated is essentiallysimilar to Table II and depicts a typical usage of the various timeslots: TABLE XVIII Time Slot No. User of Slot   1 L001 (Located in RoundLake)   2 L002 (Schaumburg)  27 L027 (Antioch)   : : 1001 1001(Arbitrary land node)   : : 1133 1133 (Lincolnshire land node)

[0263] The particular example shown in FIGS. 1 and 3, and Table III canalso be used in this explanation of Embodiment C.

[0264] Step One Call Routing

[0265] The first step of call routing for this embodiment is similar tothe step one of call routing for Embodiment A described above and TableIV can be used for this explanation. The first step is for the variousdrops to transmit a routing message in their unique time slot asdescribed above, and the message contains the information listed inTable IV.

[0266] Step Two of Call Routing

[0267] Although the number will vary, approximately 12 different nodesmight receive this transmission. Since node antennas are higher thanremote antennas, it is usually the case that node to node communicationsoccur over greater distances than remote to node communications. Signalsreceived less than 10 Db over threshold are ignored. Such signals areconsidered too weak to provide satisfactory service in a potentialmultiple link environment.

[0268] Refer to FIG. 3 and Table III. For example, node number 1193(Grayslake) might hear and record the following messages received fromvarious nodes and drops. The signal strengths and corresponding node anddrop information, exchanges, prefixes, and link numbers are loaded intoa computer memory table in the node as follows: TABLE XIX 1193(Grayslake) Exchange Prefix Link Signal Strength L001 546 1 99 L001 7401 99 L006 362 1 99 L027 395 1 99

[0269] The current measured signal strength is also added to the table.Note the following table has different signal strengths than thecorresponding table in the previous embodiment. The signal strengthswere changed to facilitate explanation. The table now appears asfollows: TABLE XX 1193 (Grayslake) Exchange Prefix Link Sig Str NewSignal Strength L001 546 1 99 31 L001 740 1 99 31 L006 362 1 99 43 L027395 1 99 24

[0270] In the above limited example, node 1193 (Grayslake) heard onlythree different transmissions from drops. These three differenttransmissions contained a total of four different prefix numbers. Aseach transmission is received the signal strength is measured andrecorded in the table above.

[0271] Step Three of Call Routing

[0272] The next step in the procedure occurs in the next cycle of thevarious time slots. Again, this step is similar to step three of callrouting in Embodiment A. Each node transmits in its unique time slot allof the prefixes that it has heard. The nodes add their own number andtransmit all of the information in the above table. For example, node1193 (Grayslake) would transmit the following during its unique timeslot. Since each node is adding a link to all tentative routes, the linknumber for each route is increased by one. Refer to Table XXI. Only aportion of the transmission is shown. TABLE XXI 1193 Land node numberL001 Exchange number 546 Prefix 2 Link number 31 Received signalstrength L001 Exchange number 740 Prefix 2 Link number 31 Receivedsignal strength L006 Exchange number 362 Prefix 2 Link number 43Received signal strength L027 Exchange number 395 Prefix 2 Link number24 Received signal strength

[0273] Step Four of Call Routing

[0274] Refer to FIG. 3. This step is similar to step four of embodimentA. Various additional nodes hear the transmission from node 1193. Theyalso hear transmissions from other nodes in their different time slots.Each node then makes a table of all the transmissions that it hasreceived. Transmissions below 10 Db are ignored. A portion of this tablemight appear as follows for node 1188. Table XXII is similar to TableVIII. TABLE XXII Table for Node No. 1188 (Libertyville) Node PrefixSignal Strength Link 1133 480 18 2 1133 362 43 1134 480 17 2 1192 546 142 1192 740 14 2 1193 546 31 2 1193 740 31 2 1193 362 43 1 1194 546 12 21194 740 12 2 1195 546 11 2 1195 740 11 2

[0275] In the above example, node 1188 heard messages from six differentnodes and drops. Included in those received messages were messages backfrom nodes about routes that already had passed through node 1188. Suchroutes are not optimum, and will be subsequently eliminated. In theprevious cycle it had transmitted that it related to exchange 362, andtwo nodes 1193 and 1133 have transmitted that information back. Note inthe above table that many signal strengths are below 30 Db. Relaxing thecriterion in embodiment A of 30 Db minimum signal strength permits manymore potential links to be considered.

[0276] At this point the new signal strength being received is added tothe table as follows: TABLE XXIII Table for Node No. 1188 (Libertyville)Site Prefix Sig. Str. New Sig Str. Link 1133 480 18 43 2 1133 362 43 431 1134 480 17 38 2 1192 546 14 17 2 1192 740 14 17 2 1193 546 31 43 21193 740 31 43 2 1193 362 43 43 1 1195 546 11 37 2 1195 740 11 37 2 1197546 12 32 2 1197 740 12 32 2

[0277] At this point the node deletes from the table every message thatit has received from an even number node. If this node would have beenan odd numbered node it would have deleted the odd numbers. In the aboveexample, two of the nodes that 1188 received from were even and they aredeleted from the table. The reason for this deletion will becomeapparent later as the problem of transmitting and receiving in the sameband is explained.

[0278] The next step is to sort the table into prefix sequence, andconsequently, all of the messages about a selected prefix will begrouped together. For example, a portion of the above table would be asfollows: TABLE XXIV Table for Site No. 1188 (Libertyville) Site PrefixSig. Str. New Sig Str. Link 1193 546 31 43 2 1195 546 11 37 2 1197 54612 32 2

[0279] The next step is to select only the best link for each prefix. Iftwo different routings contain a different number of links, the routingwith the minimum number of links is chosen. The routing with the highernumber of links is dropped from the table. Since only acceptable signalstrengths above the preselected 10 Db threshold are entered in thetable, this process selects a minimum number of links. This procedure ofdropping routes with larger number of links will reduce the number oflinks in the final route. This procedure will also reduce the number oftransmitters that are radiating power and consuming spectrum capacity.

[0280] The next step is to drop all sub-optimal links. Since receivedsignal strength is very important to signal quality, the links withinferior signal strength are dropped from the table. The strategy is todrop the route that has the worst or weakest link. In the above table,the following is the worst link: TABLE XXV 1193 31 1195 11 1197 12

[0281] In the above example, if 1188 (Libertyville) wanted to contactprefix 546, 1188 would have three choices. However, the route through1193 (Grayslake) provides the best signal strength, and consequentlythat route is chosen. The routes including 1195 and 1197 are droppedfrom the table. If two routings contained identical numbers for bothsignal strength and links, the one with the lower position in the tableis chosen.

[0282] One key point in the procedure above is that each node has thecapability through storage in its computer memory to provide at leastone route to all prefixes that can be reached with a signal greater thanthe minimum threshold as described above.

[0283] Step Five of the Routing

[0284] At this point, the computer in node 1188 (Libertyville) increasesthe link number in its internal tables. The next step is for node 1188to transmit the information in its computer memory table. As explainedabove, the node 1188 has already eliminated unsatisfactory links, andonly transmits the best link for each possible exchange. Thistransmission occurs in the next master cycle.

[0285] A portion of the transmission at this step is as follows: TABLEXXVI 1188 Land node number 546 Prefix 3 Links 31 Signal Strength

[0286] Note that node 1188 will also transmit the same messages aboutother exchanges that were received via the same and other nodes.

[0287] Step Six through “n” in the Routing

[0288] As described above in Embodiment A, node 1133 receives thetransmission from node 1188 and stores the information contained in thetransmission in its memory. Node 1133 also receives transmissions fromother nodes and other drop points near exchanges which it also stores inits memory. Node 1133 then performs the same steps that were performedby node 1188 to determine the optimum link to an intermediate node backto origin of prefix 546. This causes node 1133 to delete from its memoryall of the non optimum links, and thereby node 1133 determines that theoptimum route back to exchange 546 is through node 1188. While node 1133can not determine the total route, it can determine the best immediatelink for each exchange. Node 1133 does not store the total route.

[0289] At this point, if a mobile (remote) user in Deerfield wants touse his telephone, node 1133 is in a position to route a call to RoundLake to the 546 prefix.

[0290] Call routing is now complete.

CALL CONNECTING AND CHANNEL ASSIGNMENT

[0291] The process of using the previously created routing informationin conjunction with measured signal strengths that connects the callbetween nodes will now be explained.

[0292] In the example of FIG. 1 the mobile (remote) user in Deerfieldwants to connect to phone number prefix 546 which is in the Round Lakeexchange. The first step is for the Deerfield user to establishconnection with a node near Deerfield with an acceptable signal qualityand interference situation. This connection is established in a manneras described in U.S. Pat. No. 4,65850 and improved in U.S. patentapplication Ser. No. 08/276781 wherein several signal to interferencetests are performed. In the example in FIG. 1, this radio connection ismade with node 1133. Once this connection is established, the node 1133now must begin the process of connecting the call to Round Lake. Asexplained above, node 1133 has in its memory the node it must contact toestablish the first link in the route to Round Lake.

[0293] Refer now to FIG. 5 which shows, in additional detail, thecommunications paths between a mobile (remote) user in Deerfield and adrop near the exchange in Round Lake that handles the phone numberprefix 546. As will be appreciated, the land drop will connect to theRound Lake exchange by standard land line methods.

[0294] The system and method for setting up a call from and to the firstnode from a mobile are described in U.S. Pat. No. 4,965,850. FIG. 5shows the example of a call between a mobile (remote) user in Deerfieldand an exchange drop in Round Lake that is being routed through a totalof three different nodes. The new process of setting up the call betweenmultiple nodes will be explained hereinbelow.

[0295] As indicated in FIG. 5, for the node to node communication bands,the odd nodes have transmitters which operate in the bands where theeven nodes have receivers. Conversely, the odd nodes have receiverswhich operate in the bands where the even nodes have transmitters.

[0296] As will be more fully explained herein, the remote can originatecommunications on channel pair say 1 in bands G and H , and thecommunications from node 1133 to node 1188 will be on a channel pair say14 in bands C and D, and the communications from node 1188 to node 1193will on a channel pair say 17 in bands E and F, and the communicationsfrom node 1193 to the drop of exchange including prefix 546 will be on achannel pair say 3 in bands A and B.

[0297] Although the channels in the above tables and FIG. 5 aredesignated as voice channels, various data can be transmitted throughsuch channels as is well known.

[0298] To establish the call connection and channel selection, theprocess follows a method similar to the method for establishing a callin U.S. Pat. No. 4,965,850 and improved in U.S. patent application Ser.No. 08/276781. Tests are performed to ascertain that any channel choicewill be both interference free and non interference causing. Thechannels chosen conform to the route as explained above.

[0299] The nodes add tones/and or digital data streams to their ongoingconversations for node to node voice communications. These tones/datastreams contain the following information.

[0300] 1. Site number transmitting

[0301] 2. Site number receiving

[0302] 3. Signal strength being received.

[0303] Referring still to FIG. 5, the first step in the process is forthe first node, in this case node 1133 located in Lincolnshire toestablish a link with the next node. To facilitate this explanation, letus assume the following is the optimum route: TABLE XXVII Mobile user inDeerfield Node 1133 located in Lincolnshire (Odd) Node 1188 located inLibertyville (Even) Node 1193 located in Grayslake (Odd) Drop located inRound Lake Exchange located in Round Lake

[0304] In the above table of routings the three intermediate nodesalternate between even and odd identification numbers.

[0305] The four interference tests are now performed to establish thefirst node to node link between node 1133 and node 1188.

[0306] Test 1 Will the transmission from node 1133 interfere with anyother node receiver?

[0307] Test 2 Will node 1188 receive an interference free signal fromnode 1133?

[0308] Test 3 Will node 1188 interfere with any other node receiver?

[0309] Test 4 Will node 1133 receive an interference free signal?

[0310] As alluded to above, the node to node communications bands areBands C,D,E, and F. The selection of a channel pair between node 1133(Lincolnshire) and node 1188 (Libertyville), is independent of whethernode 1133 received this routing demand from a remote or from anothernode. The routing and channel selection process works such that therouting and channel selection process originates with node 1133 andworks towards node 1188 and node 1193.

[0311] Test 1

[0312] The Lincolnshire node 1133, which is an odd node, now mustmonitor the various channels with its scanning receiver in band D, todetermine if it transmitted in Band C whether that transmission wouldinterfere with any other node receiver. The computer controls thescanning receivers to sense the communication channels. These scanningreceivers sense the tones and/or digital data. streams that are presentin ongoing communications.

[0313] The first step is the tentative selection by node 1133 of thelowest channel pair. Site 1133 monitors the receiver channel, and if itreceives a signal on that channel, it decodes the signal information inthe tones/digital data streams, and measures the signal strength of thereceived signal. Because of signal reciprocity, that is the concept thatthe propagation path has the same loss in both directions, node 1133 cancalculate if it were to transmit in band C whether it would interferewith the paired receiver that is paired to the transmitter that node1133 just decoded. If node 1133 discovers that it would causeinterference on this tentative channel, then node 1133 steps to the nextchannel. The computer in node 1133 tunes its scanning receiver to thenext channel.

[0314] If the channel pair is acceptable, the node 1133 (Lincolnshire)transmits on that channel pair a transmission indicating the number ofthe next node 1188 (Libertyville) in the route to the final destinationfor the call. Node 1133 also adds the desired phone number and thedesired exchange to the message. This transmission is indicated in thespectrum usage table by the symbol Q. This transmission is repeateduntil terminated. The transmission includes the following: OriginatingNode 1111 Next Node in Routing 1188 Phone number of remote YYYYYYYYDesired Destination number 708-546-XXXX

[0315] Even though this channel has passed test one, it still has notpassed the other three tests. Consequently, in the meantime, node 1133(Lincolnshire) commences to step through the channels, and as it findspossibilities, turns on additional transmissions with tones and callinformation. This process of placing several transmissions on the airsimultaneously, permits the next node 1188 (Libertyville) to have aoverlapping system. A further advantage of this approach is that eventhough tests 2,3, and 4 are not passed, the next node (Libertyville)will know it has a call coming because it has received a test signalfrom node 1133 (Lincolnshire), and it can begin the test 1 process inthe alternate band towards node 1193 (Grayslake). Node 1188(Libertyville) is an even numbered node, and consequently it will usebands E and F to communicate with 1193 (Grayslake). Consequently, it ispossible that the 1188 (Libertyville) to 1193 (Grayslake) link might geta channel assignment before the 1133 (Lincolnshire) to 1188(Libertyville) link is established.

[0316] In addition the node 1133 (Lincolnshire) adds a strong tonesignal such as, for example, a 1000 cycle tone to its transmission. Theaddition of this tone will help the receivers in the other node in thescanning process. Since they are looking for a tone of 1,000 cycles,they do not need to wait and decode all transmissions. Naturally,sometimes voice, faxes, or computer communications will trigger thescanning receiver that there is a potential transmission of interest,but many times various voice messages will be quickly skipped in thatthey do not contain the indicator tone.

[0317] Refer to FIG. 12 for a detailed flow chart of the logic of thefirst test.

[0318] Test 2

[0319] Node number 1188 (Libertyville) is always in the process ofsequentially monitoring the channels in band C to determine if any oddnodes want to use number 1188 to set up a particular call. Site 1188scans the band and searches for a tone of 1,000 cycles per second. If ithears a tone of 1,000 cycles per second, the node then must determine ifthis in reality is a signaling transmission from an odd numbered node.There is always the chance that selected music, voice, or faxes wouldcreate a strong tone at that frequency. If the scanning receiver hears atone of 1,000 cycles, it decodes the message to ascertain if it isindeed a signal from test 1. This indicator tone permits the scanningreceivers to move more quickly through the band.

[0320] If node 1188 decodes the signal, and discovers that it is indeedpart of test 1, and that node 1188 is indicated to be part of an ongoingconversation, then node 1188 must begin two processes simultaneously.

[0321] The first process is to begin to perform test 1 on its transmitband E. When node 1188 (Libertyville) decodes the message from node 1133(Lincolnshire), node 1188 (Libertyville) knows a call is coming. Node1188 looks in its computer memory and notes that the next link toexchange 546 is node 1193 (Grayslake). Consequently, node 1188(Libertyville) wants to alert node 1193 (Grayslake) that it is going tobe part of a call destined for Round Lake. This transmission is similarto the transmission it just received in that it contains the nodenumbers and exchange number.

[0322] Node 1188 (Libertyville) also begins the second process of goingthrough the remainder of the four tests to finally select a duplexchannel pair that will pass all four interference tests.

[0323] To pass test 2, node 1188 only needs to determine that it will,in fact, receive a very good interference free signal on this channel.

[0324] Refer to FIG. 13 for a flow chart of the aforementionedprocedure.

[0325] Test 3

[0326] Once node 1188 (Libertyville) determines that it will receive agood signal oh the tentative channel, node 1188 must determine whetherits transmission back to node 1133 would interfere with any otherongoing communication.

[0327] Node 1188 now monitors the same channel pair in the time periodfollowing the receipt of the signaling message. It could have been thecase that 1188 received the signal on a totally quiet channel, or 1188could have received a stronger signal that temporarily masked a weakerongoing conversation. If the signal was weaker than an ongoingconversation, then node 1188 would not have decoded the signal. Sincenode 1133 and node 1188 are not located at the same place, they eachhear a different set of ongoing conversations. Although there is someoverlap in that node 1133 and node 1188 both could hear someconversations, many conversations can be heard by node 1188 that can notbe heard by node 1133, and many conversations that can be heard by 1133that can not be heard by 1188.

[0328] Node 1188 decodes any conversations that it hears looking for thesub-audible tones/data streams. Site 1188 also measures the signalstrength for the concerned signals. Site 1188 can calculate if it wereto transmit on the tentative channel, if it would cause interference atthe receiver corresponding to the transmitter that it just decoded.Since node 1188 assumes signal strength reciprocity, it can calculate ifit would cause interference in that the tones indicate the otherreceivers received signal strength.

[0329] If node 1188 determines that it would not cause interference toany ongoing communications, node 1188 signals node 1133 (Lincolnshire)that this test has passed.

[0330] Refer to FIG. 14 for a flow chart of the aforementioned logic.

[0331] Test 4

[0332] Once node 1188 (Libertyville) determines that it would notinterfere with any other communication, it transmits back to 1133(Lincolnshire) on the tentative channel.

[0333] If node 1133 (Lincolnshire) can not hear the transmission fromnode 1188 (Libertyville), it does not respond, and node 1188 triesanother channel pair.

[0334] If node 1133 hears a good signal, then it accepts this channelpair, as all four tests have passed. The channel assignment is nowaccomplished.

[0335] Refer to FIG. 15 for a flow chart of the aforementioned logic oftest 4.

[0336] This completes the channel pair assignment for the link betweennode 1133 and 1188.

[0337] Channel Assignment in Next Links

[0338] The process that node 1188 (Libertyville) goes through toestablish channel selections with node 1193 (Grayslake) are identical tothe processes just described. However, since node 1188 is an even numbernode, it does its scanning and tentative transmissions in a differentpair of bands. Site 1188 will tentatively transmit in band E and listenin band F.

[0339] Once the call reaches the final node 1193 (Grayslake), it isconnected to the drop point near the Round Lake Exchange in a mannersimilar to that described in U.S. Pat. No. 4,965,850. However, themethod in U.S. Pat. No. 4,965,850 describes a mobile initiating a callto a base.

[0340] If a node receives a connection from a remote that desires tocommunicate with a prefix that is not in the routing table, the nodewill connect the call to the drop with the least number of links in theroute as described above. Since the computer in each node knows thenumber of links to each drop, the computer can choose a nearby drop. Ineffect when a call arrives for a new prefix, the computer hasestablished a route to a nearby drop and the call is processed as above.

[0341] In most installations of the above system, the system will beinstalled in a single area code. However, to install a system in an areathat is serviced by multiple area codes, the area code and the prefixmust be utilized together as a single destination in the routing asdescribed above.

[0342] Handoff for Embodiment C

[0343] Handoff for embodiment A has been described above. Handoff forembodiment C is similar to the handoff for embodiment A except that thevarious tests of U.S. Pat. No. 4,965,850 and the improved method in U.S.patent application Ser. No. 08/276781 are used instead of the twoprocedures of embodiment A.

[0344] Embodiment D

[0345] Embodiment D is a modification of Embodiment B. Embodiment D usesthe four tests to assign channels in the corporate complex systemdescribed in embodiment B.

[0346] While the invention has been particularly shown and describedwith reference to preferred embodiments thereof, it will be understoodby those skilled in the art that various changes in form and details maybe made therein without departing from the spirit and scope of theinvention.

1-10. (Canceled)
 11. A radio communications system including a pluralityof individual nodes capable of distribution arbitrarily relative to eachother, said nodes being controllable independent of a central computerseparate from said nodes, each said node comprising: a transmitter fortransmitting radio signals to other said nodes and a receiver forreceiving said radio signals from other said nodes; circuitry for usingsaid radio signals to establish radio links between plural pairs of saidnodes; and routing circuitry for using an actual radio parameter of saidradio signals to assemble selected said links into a radio communicationroute between an originating node and a destination node, said routeincluding plural said links.
 12. A system as in claim 11, wherein saidrouting circuitry uses said radio parameter to assemble an optimum saidradio communication route.
 13. A system as in claim 12, wherein: saidradio signals identify each said node as being one of at least twodifferent categories that do not interfere when transmitting; and saidlinks are established only between different said categories of saidnodes.
 14. A system as in claim 12, wherein said routing circuitry usessaid radio parameter to assemble said links into multiple optimum radiocommunication routes, each having an originating node and a destinationnode.
 15. A system as in claim 14, wherein said routing circuitryassembles said optimum routes without necessarily including the samesaid node in any two said routes.
 16. A system as in claim 15, whereineach said node further comprises circuitry for detecting the strength ofsaid radio signals received from said other nodes, said actual radioparameter being said signal strength.
 17. A system as in claim 16,wherein a said link is established between a pair of said nodes onlywhen said signal strength exceeds a predetermined minimum threshold. 18.A system as in claim 17, wherein: said radio signals identify each saidnode as being one of at least two different categories that do notinterfere when transmitting; and said links are established only betweendifferent said categories of said nodes.
 19. A system as in claim 11,wherein each said node further comprises circuitry for detecting thestrength of said radio signals received from said other nodes, saidactual radio parameter being said signal strength.
 20. A system as inclaim 19, wherein a said link is established between a pair of saidnodes only when said signal strength exceeds a predetermined minimumthreshold.
 21. A system as in claim 11, wherein each said node furthercomprises circuitry for detecting the strength of said radio signalsreceived from said other nodes, a said link being established between apair of said nodes only when said signal strength exceeds apredetermined minimum threshold.
 22. A system as in claim 11, whereinsaid radio signals are transmitted by said nodes in separate time slots.23. A system as in claim 22, wherein said radio signals are transmittedby one said node simultaneously to plural other said nodes.
 24. A systemas in claim 11, wherein said radio signals are transmitted by one saidnode simultaneously to plural other said nodes.
 25. A radiocommunications system including a plurality of individual nodes capableof distribution arbitrarily relative to each other, said nodes beingcontrollable independent of a central computer separate from said nodes,each said node comprising: a transmitter for transmitting radio signalsto other said nodes and a receiver for receiving said radio signals fromother said nodes, said radio signals including routing messages;circuitry for using said radio signals to establish radio links betweenplural pairs of said nodes; and routing circuitry for using a content ofsaid routing messages to assemble selected said links into an optimumradio communication route between an originating node and a destinationnode, said route including plural said links.
 26. A system as in claim25, wherein: said routing messages identify each said node as being oneof at least two different categories that do not interfere whentransmitting; and said links are established only between different saidcategories of said nodes.
 27. A system as in claim 25, wherein: eachsaid node further comprises circuitry for detecting the strength of saidradio signals received from said other nodes; and each said link of saidoptimum route comprises a radio signal with a higher minimum signalstrength than the minimum signal strength of said radio signalcomprising any said link in any other potential radio communicationroute between said originating node and said destination node.
 28. Asystem as in claim 27, wherein said routing circuitry uses said contentof said radio messages to assemble said links into multiple optimumradio communication routes, each having an originating node and adestination node.
 29. A system as in claim 28, wherein said routingcircuitry assembles said routes without necessarily including the samesaid node in any two said routes.
 30. A system as in claim 29, wherein asaid link is established between a pair of said nodes only when saidsignal strength exceeds a predetermined minimum threshold.
 31. A systemas in claim 30, wherein: said routing messages identify each said nodeas being one of at least two different categories that do not interferewhen transmitting; and said links are established only between differentsaid categories of said nodes.
 32. A system as in claim 25, wherein eachsaid node further comprises circuitry for detecting the strength of saidradio signals received from said other nodes, a said link beingestablished between a pair of said nodes only when said signal strengthexceeds a predetermined minimum threshold.
 33. A system as in claim 25,wherein said radio signals are transmitted by one said nodesimultaneously to plural other said nodes.
 34. A system as in claim 25,wherein said radio signals are transmitted by said nodes in separatetime slots.
 35. A radio communications system including a plurality ofindividual nodes capable of distribution arbitrarily relative to eachother, said nodes being controllable independent of a central computerseparate from said nodes, each said node comprising: a transmitter fortransmitting radio signals to other said nodes and a receiver forreceiving said radio signals from other said nodes; detecting circuitryfor detecting the quality of said radio signals received from said othernodes; circuitry for using said radio signals to establish radio linksbetween plural pairs of said nodes; and routing circuitry for assemblingselected said links into a radio communication route between anoriginating node and a destination node, said route including pluralsaid links, wherein each said link of said route comprises a radiosignal of a higher quality than the quality of said radio signalcomprising any said link in any other potential radio communicationroute between said originating node and said destination node.
 36. Asystem as in claim 35, wherein: said routing messages identify each saidnode as being one of at least two different categories that do notinterfere when transmitting; and said links are established only betweendifferent said categories of said nodes.
 37. A system as in claim 36,wherein said routing circuitry assembles said links into multiple radiocommunication routes, each having an originating node and a destinationnode.
 38. A system as in claim 37, wherein said routing circuitryselects said routes without necessarily including the same said node inany two said routes.
 39. A system as in claim 38, wherein a said link isestablished between a pair of said nodes only when said signal strengthexceeds a predetermined minimum threshold.
 40. A radio communicationssystem including a plurality of individual nodes capable of distributionarbitrarily relative to each other, said nodes being controllableindependent of a central computer separate from said nodes, each saidnode comprising: a transmitter for transmitting radio signals to othersaid nodes and a receiver for receiving said radio signals from othersaid nodes, said radio signals including routing messages identifyingsaid node as being one of at least two different categories that do notinterfere when transmitting; detecting circuitry for detecting thesignal strength of said radio signals received from said other nodes;circuitry for using said radio signals to establish radio links onlybetween plural pairs of said nodes of different said categories; androuting circuitry for assembling selected said links into a radiocommunication route between an originating node and a destination node,said route including plural said links consisting solely of linksbetween different categories of said nodes, wherein each said link ofsaid route comprises a radio signal with a higher minimum signalstrength than the minimum signal strength of said radio signalcomprising any said link in any other potential radio communicationroute between said originating node and said destination node.
 41. Asystem as in claim 40, wherein said routing circuitry uses a content ofsaid radio messages to assemble said links into multiple radiocommunication routes, each having an originating node and a destinationnode, without necessarily including the same said node in any two saidroutes.
 42. A system as in claim 41, wherein a said link is establishedbetween a pair of said nodes only when said signal strength exceeds apredetermined minimum threshold.
 43. A node for use in a radiocommunications system including a plurality of said nodes capable ofdistribution arbitrarily relative to each other, said nodes beingcontrollable independent of a central computer separate from said nodes,said node comprising: a transmitter and receiver for transmitting radiosignals to other said nodes and a receiver for receiving radio signalsfrom other said nodes, said radio signals including routing messages;circuitry for establishing radio links between plural pairs of saidnodes; and computer means for using a content of said routing messagesto drop non-optimal said links and to assemble remaining said links intoa radio communication route between an originating node and adestination node, said route including plural said links.
 44. A node asin claim 43, further comprising detecting circuitry for detecting thestrength of said radio signals received from other said nodes, whereinsaid computer means uses said signal strength to establish said links.45. A node as in claim 44, wherein said computer means uses said signalstrength to assemble said links into an optimum radio communicationroute.
 46. A node as in claim 43, further comprising detecting circuitryfor detecting the strength of said radio signals received from othersaid nodes, wherein said computer means uses said signal strength toestablish said links and to assemble said links into an optimum radiocommunication route.
 47. A node as in claim 46, wherein said computermeans includes: means for controlling said node to cause retransmissionof said radio signals after said route is assembled; means forcontrolling said circuitry to reestablish said links if a said node hasbeen moved or an additional node has become available to be added to thesystem subsequent to assembly of said route; and means for assemblingsaid reestablished links based on said signal strength into a radiocommunication route between said originating node and said destinationnode, said route including plural said links.
 48. A radio communicationssystem including a plurality of individual nodes capable of distributionarbitrarily relative to each other, said nodes being controllableindependent of a central computer separate from said nodes, wherein:each said node includes (a) a transmitter for transmitting radio signalsto other said nodes and a receiver for receiving said radio signals fromother said nodes, said radio signals including routing messages, (b)circuitry for using said radio signals to establish radio links betweenplural pairs of said nodes, and (c) routing circuitry for using acontent of said routing messages to assemble selected said links into aradio communication route between an originating node and a destinationnode, said route including plural said links; said receivers includecall receiving circuitry for accepting external radio signals fromsources in addition to other said nodes; said transmitters include calltransmitting circuitry for transmitting said external signal tosuccessive nodes along said route to said destination node in accordancewith a content of said external signal; and each said node furtherincludes call hand-off circuitry for controlling said receiver and saidtransmitter to terminate reception of said external radio signal at onesaid node and initiate reception thereof at another said node withoutinterruption of reception of said external signal by said system.
 49. Asystem as in claim 48, wherein: each said node further includescircuitry for detecting the strength of said radio signals received fromother said nodes; and said routing circuitry assembles said links intomultiple radio communication routes, each having an originating node anda destination node, wherein each said link of each said route comprisesa radio signal with a higher minimum signal strength than the minimumsignal strength of said radio signal comprising any said link in anyother potential radio communication route between said originating nodeand said destination node, without necessarily including the same saidnode in any two said routes.
 50. A system as in claim 49, wherein: saidrouting messages identify each said node as being one of at least twodifferent categories that do not interfere when transmitting; and saidlinks are established only between different said categories of saidnodes.
 51. A system as in claim 48, wherein a said link is establishedbetween a pair of said nodes only when said signal strength exceeds apredetermined minimum threshold.
 52. A method of providing a radiocommunications route among a plurality of individual nodes capable ofdistribution arbitrarily relative to each other, said nodes beingcontrollable independent of a central computer separate from said nodes,the method comprising the steps of: establishing radio links betweensaid nodes using radio signals transmitted from each said node andreceived by other said nodes; and using an actual radio parameter ofsaid radio signals to assemble selected said links into a radiocommunication route between an originating node and a destination node,said route including plural said links.
 53. A method as in claim 52,further comprising the step of assembling said links into multiple radiocommunications routes, each having an originating node and a destinationnode, without necessarily including the same said node in any two saidroutes.
 54. A method as in claim 53, wherein: said actual radioparameter is the strength of said radio signals; and each said link ofeach said route comprises a radio signal with a higher minimum signalstrength than the minimum signal strength of said radio signalcomprising any said link in any other potential radio communicationroute between said originating node and said destination node.
 55. Amethod as in claim 54, wherein: said radio messages identify each saidnode as being one of at least two different categories that do notinterfere when transmitting; and said links are established only betweendifferent categories of said nodes.
 56. A method as in claim 55, whereina said link is established between a pair of said nodes only when thestrength of said radio signals exceeds a predetermined minimumthreshold.
 57. A method of providing a radio communications route amonga plurality of individual nodes capable of distribution arbitrarilyrelative to each other, wherein each said node comprises one of at leasttwo different categories and is controllable independent of a centralcomputer separate from said nodes, the method comprising the steps of:establishing radio links between said nodes using radio signalstransmitted from each said node and received by other said nodes;deleting said links between nodes of the same category; and assemblingselected remaining said links into a radio communication route, saidroute including plural said links.
 58. A method as in claim 57, whereinsaid radio signals are transmitted by one said node simultaneously toplural other said nodes.
 59. A method as in claim 57, wherein said radiosignals are transmitted by said nodes in separate time slots.
 60. Amethod of providing a radio communications route among a plurality ofindividual nodes capable of distribution arbitrarily relative to eachother, said nodes being controllable independent of a central computerseparate from said nodes, the method comprising the steps of:establishing radio links between said nodes using radio signalstransmitted from each said node and received by other said nodes;assembling selected said links into an optimum radio communication routebetween an originating node and a destination node, said route includingplural said links; and changing said route between said originating nodeand said destination node only when a condition of the route changes.61. A method as in claim 60, wherein said radio signals are transmittedby one said node simultaneously to plural other said nodes.
 62. A methodas in claim 60, wherein said radio signals are transmitted by said nodesin separate time slots.